The present invention relates to a current-pressure transducer, particularly for a vacuum control in automotive vehicles, having a vacuum chamber divided by a membrane with a double valve on one side of the membrane activatable by pressure on the membrane, and including a solenoid activatable valve on the opposite side of the membrane and connected to the membrane.
Such current-pressure transducers can be used in exhaust gas return systems and in a turbo-charger control for controlling the bypass valves.
Features of current-pressure transducers of this type are known a vacuum regulator for vacuum systems, in particular for the testing of ignition distributors with double vacuum displacement, in which a single vacuum pump and two such vacuum regulators are used (Federal Republic of Germany OS 21 09 597). One chamber of this vacuum regulator is provided with a connection for supply vacuum as well as with a connection to receive an adjustable controlled vacuum. The chamber is closed off on one side by a membrane which is connected, via a spring, to a threaded rod which, in its turn, rests via a knurled nut against an extension of the chamber. Depending on the adjustment of the threaded rod, a greater or lesser force is exerted on the membrane. The position of the membrane depends on this force and on the vacuum prevailing in the chamber as compared with the external pressure (atmospheric pressure). Via a double-armed lever, the membrane acts on a first valve member, which is developed as a ball and rests within the chamber against a conical valve seat, and on a second valve member, also developed as a ball, which is arranged outside the chamber. A compression spring urges the second valve member at all times towards the corresponding valve member. The first valve member is moved by the vacuum in the chamber against its valve seat as far as the deflection of the membrane permits. The second valve member then lifts off from its seat and establishes a connection between the chamber and the outer pressure (atmospheric pressure) when the knurled nut is displaced in the direction towards lesser vacuum in the chamber. The second valve member then closes again when the vacuum in the chamber has reached the predetermined value.
It is, to be sure, conceivable to replace the threaded rod, the spring and the knurled nut of the known pressure regulator by an electromagnet with plunger-type armature in order to control the vacuum in the chamber, and thus the available control pressure, as a function of the current with which the said electromagnet is energized. This, however, still does not provide any teaching as to how a pressure-current characteristic of such a current-pressure transducer can be controlled in such a manner that this characteristic becomes steeper or less steep. One could at most think of replacing the spring between the threaded rod and the membrane, but by this only a stepwise adjustment of the characteristic is possible.